The present invention relates to pain management. In particular, the invention relates to intramuscular stimulation therapy utilizing pin penetration and electrical stimulation to help relieve acute, subacute and chronic nerve-related pain for which a specific cause cannot be determined, and for which medicinal and other usual methods of pain relief have proven ineffective, i.e., neuropathic pain. It will be understood that, except as otherwise indicated, "pain" as used herein broadly encompasses severe pain as well as discomforts and early manifestations of pain such as muscle soreness, stiffness, achiness, tightness, tenderness and fatigue.
Conventional pain management is directed toward treating the symptom and not the cause of pain. Conventional methods of treating pain include, as broad categories: (1) medications, (2) physical therapy, (3) chiropractic manipulation, (4) epidural injections or nerve-root blocks, and last but not least (5) surgery. Most of these techniques can be used only for a limited number of times and are not helpful in the long-term management of chronic myofascial pain. The management of chronic pain due to repetitive strain injuries is a $120 billion dollar business in the United States, by 1994 estimates of the U.S. Occupational Safety and Health Administration (OSHA). Low back pain alone is a leading cause for physician visits, second only to the common cold. Neurophysiologically and anatomically based pain management methods which do not use drugs are an effective alternative to conventional care.
As described in the present inventor's copending application Ser. No. 08/856,064 (hereby incorporated by reference in its entirety), non-chemical, non-electrical intramuscular stimulation (IMS) is used effectively in the management of regional and diffuse myofascial pain (fibromylagia) of radiculopathic origin where musculoskeletal pain resulting from muscle shortening is the predominant feature. Unlike acupuncture, where many pins which remain stationary are inserted into points on imaginary meridians, in IMS generally only one pin is used at a time. The pin, which is inserted into a tender muscle motor point, is continuously manipulated to achieve pain relief. The IMS technique was pioneered by C. Chan Gunn, M.D. and is described in the following publications, each of which is, in its entirety, incorporated by reference herein: Gunn C. C. et al., Dry Needling of Muscle Motor Points for Chronic Low-Back Pain, A Randomized Clinical Trial With Long-Term Follow-Up, Spine, Vol. 5 No. 3, May/June 1980, pp. 279-291; Gunn C. C., The Gunn Approach to the Treatment of Chronic Pain--Intramuscular Stimulation for Myofascial Pain of Radiculopathic Origin, 2d Ed., Churchill Livingston, London, UK (1996).
Building on the work of Gunn, and based upon a clinical study of pain relief experienced by patients who have undergone electromyography (EMG) to determine the effects of IMS on pain symptoms, the present physician inventor developed and has used with success a modified IMS technique--twitch obtaining IMS. In EMG, a pin electrode is inserted into muscles for detection of electromyographic signals. During EMG, the pin is moved in all directions for examination of the electrical activity of the muscle during rest, and minimal and maximal contraction. The inventor's modified IMS technique (twitch obtaining IMS) focuses on eliciting twitch responses from muscles by stimulation of motor end plate zones, as opposed to stimulation of motor points as described by Gunn. In the inventor's original technique, a somewhat randomly directed needle insertion was followed with needle movement in all directions and at different depths in the muscle, as in EMG studies, in order to localize and accurately position the pin in the motor end-plate zone. See Chu J., Myofascial Pain Syndrome--Trigger Points, J Musculoske. Pain, 5(1):133-135, 1997; Chu J., Does EMG (Intramuscular Stimulation) Reduce Myofascial Pain Due To Cervical Radiculopathy, Electromyogr. Clin. Neurophysiol. 37:259-272, 1997; Chu J., Twitch-Obtaining Intramuscular Stimulation: Its Effectiveness in the Long-Term Treatment of Myofascial Pain Related to Lumbosacral Radiculopathy. Arch. Phys. Med. Rehabil. 78:1024, 1997; Chu J., Twitch-Obtaining Intramuscular Stimulation: Effective for Long-Term Treatment of Myofascial Pain Related to Cervical Radiculopathy, Arch. Phys. Med. Rehabil. 78:1042, 1997; and Chu J., Dry Needling (Intramuscular Stimulation) in Myofascial Pain Related to Lumbosacral Radiculopathy, European J. Phys. Med. Rehabil. 5(4):106-121, 1995 (each publication hereby incorporated by reference in its entirety). Later, the present inventor observed that increased pain relief effects could be obtained by needling muscle tender points with a simple in-out motion of a needle along the myofascial bands of the muscles.
In contrast to conventional pain management, IMS, and particularly twitch obtaining IMS, is an effective procedure which can be used repetitively throughout the lifetime of the chronic pain patient, without endangering the health of the patient or causing substantial adverse side effects. The pins used generally cause little trauma, and tissue damage, if present, is generally microscopic. IMS, particularly twitch obtaining IMS, has the capacity to help patients in chronic pain on a mass, world-wide scale, as regional and diffuse myofascial pain, e.g., due to aging of the spine causing spondylitic radiculopathy, is a ubiquitous problem.
IMS, and particularly twitch obtaining IMS, treats the cause of the pain, i.e., muscles shortened or in spasm due to nerve root irritation. When the muscles are shortened due to spasm from nerve root irritation, the muscles pull or tug on adjacent structures to which they attach such as tendons, ligaments, bones, joints, and intervertebral discs. They also pull on the intramuscular blood vessels and nerves. This unrelentous pulling of the shortened muscles causes more nerve root irritation and resultant muscle shortening leading to a vicious cycle of acute, subacute or chronic nerve related pain. By causing the muscles to twitch with the stimulation of the pin, the shortened muscles are stretched and exercised from within the muscle leading to muscle relaxation. Muscle relaxation in turn leads to less tugging effect on the pain sensitive tendons, ligaments, bones, joints, intervertebral discs, onto which these muscles attach, and therefore pain reduction is achieved. Successive treatments lead to more muscle relaxation allowing the intramuscular nerves to heal by restoration of circulation to muscles and nerves.
IMS has until recently only been performed manually. In accordance with Gunn's teaching, a thin flexible acupuncture needle (pin) is inserted into the patient's flesh utilizing a tubular guide. The pin is attached at its proximal end to a distal end of a plunger which is reciprocable within the guide. The plunger protrudes from the proximal end of the tubular guide to provide a finger grip surface, whereby the plunger (and attached pin) can be advanced and retracted. An example of such a tubular guide is the Showa #6 available from Nikka Industries Ltd., Vancouver, B.C., Canada. In accordance with the inventor's modified manual IMS technique twitch obtaining IMS, the same type of tubular guide can be used. However, a stiffer EMG needle is preferred for certain applications.
Despite their effectiveness in ultimately providing pain relief, manual IMS treatments can be quite painful to the patient. The pain is primarily due to the irregular deflection of the pin from its proper path as it is manually pushed in and pulled out repetitively through tissues of differing resiliencies. With the manual method of IMS, it is difficult to maintain proper positioning and directivity of the pin insertion with each to and fro movement, because of the manual effort required of the physician. As a result, the twitch point is easily lost. In such a situation, the pin direction is changed (often several times) within the muscle in order to return the pin to the vicinity of the twitch point. This causes significant additional discomfort to the patient, as well as increased bleeding and tissue trauma. Uneven starts and stops within the muscle are also inevitable because the movements are dependent on the treating physician's skill and strength on encountering different resistance of skin, subcutaneous and muscle tissue at any given point. Less pain would be experienced by the patient if the pin movements could be kept regular, even and steady.
In addition, the work involved on the physician's part in performing manual IMS is laborious, tedious, time-consuming and likely to lead to repetitive stress injury. This is due to the repetitive and resisted upper extremity movements required in performing the procedure. The problem for physicians is particularly acute when, as is typically the case, many areas of a patient's body are to be treated in one session, and when the majority of the patients require this type of multi-area treatment. Under these circumstances, physicians performing manual IMS on a long term basis likely will suffer from repetitive strain injuries and eventually have to stop practicing the method.
With the inventor's manual twitch obtaining IMS modality, physical manipulation of the pin (primarily pin reciprocation) is continued at a treatment point until the muscle is fatigued and cannot respond to the reciprocating pin. (twitch exhaustion). Twitch exhaustion by pin manipulation is time consuming. Typically, there may be as many as 5-100 twitches at a given twitch point before the muscle becomes refractory to further stimulation by pin manipulation. In addition to the repetitive stress injury that may be caused to the therapist, typically, it is only possible to treat four twitch points per muscle and a total often muscles within an allotted treatment time of 30-40 minutes. Thus, many treatment sessions may be required to treat all of the afflicted areas. In addition, since the manual method seeks to elicit all twitching at a given point, the pin is usually moved in all four major quadrants and subquadrants in order to evoke the twitches. These movements cause more tissue trauma and pain to the patient
To alleviate the aforementioned problems with manual IMS procedures, particularly twitch obtaining IMS, the present inventor (along with her coinventor) Zen Guo Yan) developed the automated tool and technique which are the subject of U.S. patent application Ser. No. 08/856,064, filed May 14, 1997. In that technique, a needling device providing automated pin insertion, reciprocation and retraction is pre-positioned for pin penetration at a chosen site on a patient's skin. The automatic needling device is controlled to automatically advance a pin thereof to a predetermined penetration depth within the patient's flesh, reciprocate the pin back and forth through a predetermined stroke length a predetermined number of times (e.g., 3-4), and retract the pin from the patient's flesh, while the needling device is maintained at the chosen site. Before movement to another site, the cycle is typically repeated up to three times. (Of course, early termination may be required due to patient pain or discomfort, or in the event that the muscle is or has become refractory to further stimulation.)
While the inventor's automatic needling device and method represents a substantial improvement over previous needling instruments and IMS methods, patient pain and tissue trauma could be reduced even further if the requirement of physical pin manipulation (e.g., reciprocation, etc.) to obtain twitches could be substantially reduced or eliminated. Maintenance of the pin at a proper position (for eliciting twitches at the motor end plate zones) would also be facilitated by reduced needle manipulation.
The present physician inventor has found twitch obtaining IMS (both manual and automatic) to be very effective in the acute and long term management of nerve related pain. However, effective twitch obtaining IMS in accordance with the inventor's previous manual and automated modalities is learned through a period of apprenticeship requiring up to a year at least. This limits the number of physicians who can be trained in this method. The device of the present inventor's application Ser. No. 08/856,064 facilitates the training of persons in the technique. However, even with automation of the method, mastery of the technique, including the ability to precisely locate the motor end plate zones and then stimulate the same to elicit twitches, is obtained only after a rigorous and prolonged training period. It would be highly beneficial if the technique could be simplified such that it could readily be taught, not only to doctors, but also to paramedical personnel such as nurses and physician assistants. Such personnel could treat less involved patients as well as institute treatments earlier, leading to increased prevention of chronic pain. This would result in real savings in direct and indirect health care costs, and the technique could be offered more effectively to patients on national and international levels.
Electrical stimulation has been used in muscle diagnostic procedures, e.g., single fiber electromyography (SFEMG). See Stalberg et al., Single Fiber Electromyography, Studies in Healthy and Diseased Muscle, 2d Ed., Raven Press Ltd., New York (1994). In SFEMG, electrical stimulation is used to selectively and reproducibly activate motor axons, and this activity is recorded by a separate micro-electrode to detect neuromuscular transmission disorders. Such micro-electrical stimulation is carried out using a cathode in the form of a monopolar pin insulated to near the tip (e.g., Medelec MF37 Teflon coated monopolar pin). The pin is supplied with pulsed current of short duration (10-50 .mu.s) with either constant current or constant voltage. Amplitudes of 0.5 to 10 milliampere (0.5-30 volts in the case of constant voltage output) have been described. The rate of stimulation has been described to be 10-50 Hz. The reference electrode is a similar needle placed subcutaneously about 15-25 mm away or a surface electrode (e.g., plate or strip such as used for grounding). The positioning of the stimulating electrode is done to obtain a relatively weak stimulus in order to elicit twitches in a small portion of muscle, visible as fine jerking of the stimulating needle or as fasciculation-like twitches. Stronger jerks (elicited from positions near a major nerve branch) are suggested to be avoided as such stimulation activates many motor units and makes selective recording with the SFEMG electrode difficult.
One use of SFEMG is to determine the conduction time across the motor end-plate zones for diagnosis of degenerative muscle diseases such as myasthenia gravis. Correct placement of a recording micro-electrode at the motor end-plate zone for this procedure is accomplished through micro-electrical stimulation to elicit a twitch serving to identify the motor end-plate zone.
Electrical stimulation has also been used to augment needle based pain relief treatments, including acupuncture and IMS therapy.
In electro-acupuncture, acupuncture pins serving as electrode pairs are supplied with constant or pulsed direct current. The pins are placed into traditional acupuncture points along traditional imaginary meridians.
Gunn teaches in his 1996 text, supra, that electrical stimulation can be used in his IMS technique (focused on stimulation of clinical muscle motor points), in place of manual needle agitation, to hasten the release of muscle contracture (pp. 12 and 35-36). Specifically, Gunn teaches (at page 35) that a low-voltage (9-18 V) interrupted direct current may be administered for seconds or minutes to the inserted needle until muscle release is obtained. Gunn further teaches alternatively that the electrical stimulation may be applied for approximately 15-30 minutes, with the current being gradually increased until muscle contractions are visible to confirm that the needles are properly placed.
The standard acupuncture pins used in electro-acupuncture and Gunn's IMS technique are conductive along their entire lengths. As a result, the electrical field which is established extends along the length of the inserted portion of the pin, and is dispersed into the skin and subcutaneous tissues, in addition to the target muscle area. The intensity of the electric field actually established at the target area is difficult to accurately calculate and control.
Any twitch responses obtained by use of these techniques are generally of relatively small size (i.e., microtwitches). As previously described, in contrast to twitch obtaining IMS, these techniques are not focused on elicitation of strong multiple twitches at muscle motor end plate zones. Gunn's method seeks to cause muscle contracture and release (not twitches per se) by stimulation at clinically defined muscle motor points (as opposed to anatomically defined motor end plate zones) and does not account for the present inventor's discovery that the therapeutic effect of the twitches increases with the size and number of the twitches. In electro-acupuncture, since the acupuncture points are located along traditional imaginary meridians, they may or may not coincide with the twitch points. The duration of time for electrical stimulation is not standardized and may vary from a few seconds to approximately twenty minutes, depending on the acupuncturist's style and subjective/empirical evaluations.
The present inventor has found that elicitation of twitches in twitch obtaining IMS is facilitated by initially causing the muscle to be treated to relax. This can be performed using physical agents such as heat, ultrasound, or electrical stimulation. In addition, oral ingestion of muscle relaxants or anti-anxiety agents, such as Valium (5-10 mgm), and a pain medication, such as 1-2 tablets of Percocet (Oxycodone 5 mg, and Tylenol, 375 mg/tablet) or Morphine Sulfate Immediate Release (MSIR), 15-30 mg, 1 hour before treatment can be used. Of all the physical agents that could be used to relax a muscle in order that twitches can be more easily evoked, the present inventor has found electrical stimulation to be the most effective.
For a time beginning in December of 1994, the present inventor supplemented her manual twitch obtaining IMS modality with electrical stimulation in the treatment of patients. In that technique, the electrical stimulation was supplied by surface mounted (skin patch) electrodes receiving a bi-polar exponential decaying current pulse train from a commercially available electronic waveform generating instrument (the H-WAVE, Electronic Waveform Lab, Huntington Beach, Calif.). The electrical stimulation created a relatively wide area electrical field serving to enhance the elicitation of twitch responses generated primarily by manual manipulation (e.g., reciprocation) of a non-electrified pin inserted into a muscle motor end plate zone. As in the inventor's non-electrified manual and automated IMS techniques, twitches were elicited with an acupuncture pin reciprocated with a metal plunger within a tubular guide placed at the twitch point (above the motor end-plate zone). Twitches at a given motor end plate zone generally would be exhausted by in-out reciprocation of the needle before moving on to treat another motor end plate zone. With this technique, maintenance of the pin at the twitch point was difficult since the plunger could not be stabilized adequately, often causing significant sway of the pin away from (and loss of) the twitch point. In addition, the amount of electrical stimulus needed to make the muscle twitch was difficult to assess due to the indirect stimulation provided by the skin-patch electrodes. Ultimately, the present inventor found the technique to be too cumbersome to be used effectively on a routine basis.